Need help locating Transfer (OIL) Pressure Switch

I need some help. Reference the attached file for details. 1992 4runner 3.0 automatic transmission with the A.D.D system. I'm in the process of troubleshooting my four-wheel drive and suspect this switch is not functional. I have looked everywhere, nothing on the vehicle resembles it. Any help would be appreciated.

 

I've only worked on the manual, but these are a few figures from the FSM and a google search that I hope are of some help. Best of luck.

 

Watermelon Man,
Thank you for the reply. I reviewed the information supplied, while very informative, not exactly what I am needing. I have a factory service manual with wiring diagrams that include wire bundle routing, splice, connector and component locations. The only items I am not able to check are the diode and transfer oil pressure switch. After a lot of wiring repairs, as the wiring has degraded over time. I am able to get 4H to engage with no indicator light on the dash and when I engage 4L, it also works except the 4X4 rapidly flashes and I can hear the 4WD relay firing along with the flashing. I am wanting to replace the whole dang harness.

 

did you ever figure this out? This is the only place on the whole internet ive found this switch mentioned. I'm pretty sure there's an issue with mine. Solenoids check out. When you start the vehicle it immediately energizes the ADD relay. If I could find this pressure switch I could check it.

 

it looks like it should be pretty dang obvious but I sure cant find it!